1. Field of the Invention
The invention relates generally to the production of insulated glass units (“IGUs”) for windows and, in particular, to the production of IGUs for custom windows.
2. Background Information
Known prior production systems for insulated glass units (“IGUs”) for custom windows include a number of stages or stations, for example, a glass cutting station, a glass washing station, one or more assembly stations in which spacers are matched to the glass, and as a final stage a heated roller press station. Typically, the IGU production run is scheduled each day, based on the various customer orders and the associated shipping requirements, and also on the thickness of glass that is being cut on a given day. The IGUs are scheduled in batches, and within each batch the respective IGUs are produced in the same order in which the finished windows will ultimately be shipped or bundled for delivery.
When the IGUs are completed, they are then sent to the various other production processes, such as a vinyl fabrication process and a glazing process, which similarly take up the IGUs in the order in which the corresponding windows ship. Accordingly, at the end of the final process, the respective windows can be readily packed for shipping as the windows are completed. The windows thus do not require further sorting or storing and/or the associated extra handling. The potential for damage to the completed windows and the need for storage space for the custom-order windows is therefore minimized.
To produce the IGUs, an insulated glass sheet is cut into appropriately sized pieces, with matching pieces cut for each of the respective IGUs. The glass sheet is typically cut in a manner that optimizes the use of the glass. After cutting, the pieces are broken out of the sheet and the cut glass pieces for a given IGU are grouped together and the groups are then sorted into the production order. To sort the cut glass, the workers place the pieces for a given IGU in a designated slot of a particular production, or harp, cart. Each harp cart holds the cut glass for approximately 100 IGUs, and each batch of cut glass corresponds to approximately 400 IGUs, or the contents of four carts. If the cut glass breaks or is otherwise damaged during the breakout, sorting or carting steps, repair glass is cut and placed in the appropriate cart/slot. Once the carts are filled, the carts are moved to the washer station, and the cut glass pieces are removed from the carts and sent through the washer in the sorted order.
After washing, the glass is provided to the assembly stations where spacers are matched to and combined with the glass. At the assembly station the spacers are arranged on a first of the cut glass pieces and the second piece of cut glass is then placed on top of the spacers, such that the spacers are sandwiched between the two pieces of cut glass. The glass “sandwiches” are then sealed at a next station by heating and pressing. Thereafter, the assembled IGUs are labeled and returned to the carts, still in the sorted order, and the carts then transport the IGUs to the fabrication and/or glazing processes.
The end result of the production method described above is that the IGUs, and ultimately the finished windows, are made in an order that corresponds to how the windows must be arranged for shipment. The windows can thus be readily moved off of the production line to trucks or containers for shipping, as discussed above.
One of the disadvantages of the production method is that the steps of carting and un-carting the cut glass have the potential for scratching or breaking the glass. In particular, when the two cut pieces of glass are grouped, the two pieces may scratch one another. Also, when the two pieces are placed on end in the cart, the pieces may scratch as they ride against each other and/or the pieces may break at the corners or along the ends on which they rest in the cart. Further, when the glass is pulled out of the cart for washing, there is again the risk of scratching and/or breaking. Also, when low-E glass is used, the carting and un-carting of the glass may introduce smudges and/or fingerprints that are not easily removed. Additionally, the carting and un-carting steps involve a risk of cuts or other injuries to the workers who handle the glass and/or maneuver the heavy carts.
Another disadvantage is that the various stations tend to operate at different paces, in the sense that the cutting, breaking out and sorting process takes longer than the respective washing and assembly processes. After the cutting and sorting process, the glass for approximately 400 windows essentially arrives by cart at the washing station at one time. The glass is then relatively quickly removed from the carts and serially fed into the washer. The washed glass is then provided directly to the spacer assembly station at a is relatively rapid rate. The assemblers must work quickly to assemble the glass and spacers, to keep pace with the arrival of the washed glass. After the batch of IGUs are assembled, the assemblers are then idle until a next batch arrives at the washer. The intermittent and rapid pace of the assembly work tends to increase the potential for repetitive motion injuries.